After undergoing an exercise stress test to determine whether they were appropriate for this study, as well as to determine maximal physiological responses, 15 men and 15 women, age 20 to 40 years, participated in this study to compare peak cardiovascular responses to concentric versus eccentric exercise on the Biodex* isokinetic dynamometer. Concentric exercise on the Biodex involved extension and flexion of joint against the resistance of the torque arm, and eccentric exercise involved resisting the force of the torque arm aimed at extending and flexing a joint. Heart rate, blood pressure, rate-pressure product, and electrocardiogram data were collected during and immediately after the exercise. Maximal concentric and eccentric contractions of the quadriceps and hamstring muscles of the subject's dominant leg were performed during one testing session on the Biodex at speeds of 60, 90, and 120 degrees per second and 90, 120, and 180 degrees per second for eccentric and concentric modes, respectively. There were 30-second rest periods between sets and 30 minutes rest between modes. Results are being analyzed to determine differences in the peak cardiovascular parameters between concentric and eccentric exercise. The results of this study will provide physical therapists with an understanding of how exercise on isokinetic devices affects the cardiovascular system so appropriate and safe exercise regimens can be designed. Data still under analysis.